Systems and methods for using additive manufacturing for thermal management

ABSTRACT

According to one embodiment, a thermal management system for electronic devices, including a heat frame, a conformal slot portion, chassis frame, and heat fins wherein the heat frame, conformal slot, chassis frame, and heat fins are integrally formed as a unitary structure by additive manufacturing. In another example, there is a modular vapor assembly for electronic components having a vapor chamber comprising a component surface and a top surface with a vapor channel formed therebetween with at least one liquid receptacle and having a wick structure on at least some of an interior of the component surface. In operation, there is a circuit card with at least some of the electronic components coupled to the vapor chamber component surface and the wick structures transfer at least some of the liquid from the receptacle towards the electronic components, wherein the liquid turns to a vapor that moves towards the receptacle.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.14/592,387, filed Jan. 8, 2015, now allowed, which claims the benefit ofU.S. Provisional Application No. 61/976,649, filed Apr. 8, 2014.

BACKGROUND

The operation of electronic devices requires satisfactory thermalmanagement to ensure proper function. As the electronic devices becomeheated, the devices suffer from device degradation, functional failure,and lower lifespan.

For example, the capability of avionics electronics is determined by thecomputing processing ability of the system. Typically there are size andweight constraints for an avionics system. These systems are thermallylimited such that, for a given volume, only a certain number of cores orprocessors can operate before thermal issues such as overheating occurs.Typically, processors are de-rated (up to 80%) to avoid overheating inhigh ambient temperature environments—drastically reducing capability.If the heat can be effectively removed from the system, more processingpower, and ultimately more processing capability, is possible from thesame volume and weight.

There are a number of conventional cooling methods such as fans andheatsinks that are currently used to remove heat from the electroniccircuitry and maintain the operational temperature range for theelectronics. Technological improvements have continued to increase thedevice density and reduce packaging while also increasing the computingpower and functionality such that thermal management systems are a keyoperational element. In addition, certain applications have restrictionsin the size and weight that limit the cooling capacity and thereforelimit the processing power and functionality of the electronics.

Some improved advances include heat pipes and synthetic jet cooling.Heat pipes provide for some efficiency improvements in the thermalcharacteristics whereas synthetic jets essentially provide for improvedreliability relative to fans.

System designers have increasingly recognized that the thermalmanagement is a critical factor to the successful deployment ofelectronics and currently design assemblies and systems in order tooptimize thermal performance.

The thermal path from the electronic component to the cold reservoir islimited by current technology. Certain conventional designs include theuse of milled aluminum heat frames, composite materials for chassis andmounting electronics closer to the cold reservoir. Further aspectsinclude integrating planar vapor chambers and linear heat pipes into aheat spreader structure.

What is needed to further enhance processing power and functionality isto improve the thermal performance.

SUMMARY

The thermal management system for electronics according to one exampleincludes a heatframe, heat fins and/or heat exchanger, chassis portionand conformal slot portion integrally formed as a vapor chamber by 3Dprinting. In further embodiments, any 3D vapor chamber formed by theadditive manufacturing processes as detailed herein is within the scopeof the system. A further example includes a heat exchanger or cold platethat interfaces with the vapor chamber or chassis. In certainembodiments, the 3D vapor chamber has a 3D wick structure formed oninternal surfaces. There can also be 3D support structures integratedinto the 3D vapor chamber, wherein the support structures in one examplefacilitate the transfer of liquids and gas.

In one example, the vapor chambers are modular such that multiplechambers are coupled together to form a chassis. The chassis can includean input/output (I/O) interface that electrically connects theelectronics on a circuit card to the external environment.

A further embodiment is a closed 3D vapor chamber having a heatframewith a component side and an opposing side with a vapor channel formedtherebetween. There is at least one liquid receptacle on a first sideend of the vapor channel, and typically a liquid receptacle on theopposing side end. A plurality of wick structures are interiorlydisposed on at least some of the component side and the opposing sideand heat fins and/or heat exchanger is disposed on an exterior of the 3Dvapor chamber.

These and other aspects, features, and advantages of this disclosurewill become apparent from the following detailed description of thevarious aspects of the disclosure taken in conjunction with theaccompanying drawings.

DRAWINGS

Embodiments described herein will become better understood when thefollowing detailed description is read with reference to theaccompanying drawings in which like characters represent like partsthroughout the drawings, wherein:

FIG. 1A and FIG. 1B shows a conventional circuit card assembly withelectronic components on a circuit card mated to a heat frame;

FIG. 2 is depicts the conventional circuit card assembly including theelectronic circuit card, heat spreader, wedgelock, chassis and fins;

FIG. 3 shows a conventional chassis for housing circuit card assemblies;

FIG. 4 illustrates one embodiment of the present system that includes anintegrated assembly providing thermal management for an electroniccircuit card;

FIG. 5 shows the thermal flow path in a conventional chassis withattached circuit card assembly;

FIGS. 6A and 6B depict the modular vapor chamber according to oneembodiment;

FIG. 7 shows another embodiment of the modular vapor chamber with twocircuit cards;

FIG. 8 is another example of the modular vapor chamber and variousnon-uniform wick structures;

FIG. 9A shows another example of the modular vapor chamber havinginternal supports in accordance with another embodiment;

FIG. 9B shows a modular vapor chamber embodiment with wick structuresfor enhanced support and fluid flow;

FIG. 9C shows a modular vapor chamber embodiment with internal supportstructures that may also serve as feeder arteries for the liquid;

FIG. 10A-10G depicts various embodiments of the structuralcharacteristics for the internal supports for the 3D vapor chamber;

FIG. 11A-D depicts several examples of the non-uniform wick structure;

FIG. 12A-12B show modular vapor chamber embodiments with integratedhollow fins;

FIG. 13 shows thermal management system as a vertical assembly includingseveral vapor chambers assemblies vertically assembled to form thechassis portion;

FIG. 14A-D shows stacked modular vapor chambers and assembly intoavionics system with I/O module;

FIG. 15 shows embodiment with enhanced convection using synthetic jetslocated in bottom tray and on top of I/O module;

FIG. 16A-C shows modular vapor chamber in another embodiment that isintegrated into the airframe skin;

FIG. 17A-C shows modular vapor chambers in alternate stackingconfigurations;

FIG. 18 shows a thermal management system as a planar assembly includingtwo or more of the vapor chambers planarly assembled to form the chassisportion;

FIG. 19A-C shows various surface geometry of the 3D vapor chamber toenvelop the circuit electronics including conformal, reverse-conformaland custom-conformal configurations;

FIG. 20 shows a thermal management system with a compartmentalized vaporchamber including several compartments partitioned within the same vaporchamber and adjacent to each other; and

FIG. 21A-F is another example of the modular vapor chamber withcomplaint wall and wick structures.

DETAILED DESCRIPTION

Example embodiments are described below in detail with reference to theaccompanying drawings, where the same reference numerals denote the sameparts throughout the drawings. Some of these embodiments may address theabove and other needs.

The thermal management system in one example describes a thermalmanagement device comprising a sealed vessel that contains a workingfluid. A specially engineered internal structure within the sealedvessel interacts with the working fluid to enhance the transfer of heatenergy. The vessel is of a conformal, reverse-conformal orcustom-conformal shape as required by the specific application. One partof the internal structure includes fine structures engineered to providestrong capillary forces to the working fluid at locations where they arerequired. Other parts of the internal structure include fine structuresengineered to transport the working fluid with minimal pressure dropwhile preventing interference with the vapor state of the working fluid.Additional support structures, as part of the internal structure act tointernally support and strengthen the sealed vessel, and thereby toprovide additional paths for fluid transport. Working components,usually electronic, that generate parasitic heat losses are thermallyconnected to the thermal management system. In effect, the thermalmanagement system establishes a specially engineered thermal pathbetween the electronic components and a cold reservoir and therebytransfers the heat from the components to the cold reservoir.

FIG. 1A and FIG. 1B shows a conventional circuit card assembly withelectronic components on a circuit card mated to a heat frame. Referringto FIGS. 1A and 1B, a conventional circuit card 10 is shown in FIG. 1Awith electronic components 20 that can include components such asprocessors that generate considerable heat. Referring to FIG. 1B, inmany applications the circuit card 10 is coupled to a heat spreader card50 by flipping the circuit card 10 and securing it to the heat spreader50 so the components 20 are proximate the heat spreader 50. While thisform of heat dissipation works to some degree, it can only dissipate acertain amount of heat generated by the components 20 and requires alarge and bulky heat spreader 50. As the processing capabilities haveincreased, the individual components have decreased in size and requireeven greater heat dissipation capabilities in a smaller space.

FIG. 2 depicts a conventional thermal management system 200 according toone example for an assembly (not shown). In such a conventional system,the components such as the heat frame or heat spreader 240 withwedgelock 250 and circuit card 210 coupled thereto are mated to thechassis frame 260 having fins 270. In the state of the art, electroniccomponents 220 are mounted to a component board 210 such as a printedcircuit card/board (PCB). The components 220 typically have a thermalinterface material (TIM) 230 to transfer the heat from the components220 to the heatframe 240, particularly since the components 220 may havedifferent shape/size and the heatframe 240 is configured to allow forthe highest component height. The heatframe 240 is typically constructedof a material such as aluminum to provide for efficient heat transfer ofhas a sufficient size to facilitate the heat transfer.

As noted in FIG. 2, components 220 generate heat that is conductedthrough TIM 230 to the heatframe 240. The heatframe 240 further spreadsthe heat to the wedgelock 250, to the chassis frame 260 and then to thefins 270. Thus, the heat is finally dissipated to the environment andfins 270 are designed to be large enough to dissipate the expected heatfrom the electronic components.

In some cases, the heatframe 240 can be quite large in comparison to thecircuit card 210. The wedgelock 250 is used to seat the heatframe 240(pre-assembled with the card 210) into the chassis frame 260 wherein thechassis frame 260 has a mating portion for the wedgelock 250, forexample a chassis groove, to receive the wedgelock 250. The wedgelock250, in certain examples, is a cam operated device that serves to lockthe heatframe 240 to the chassis frame 260. Chassis frame 260 typicallyhas fins 270 to allow for a greater surface area so the externalenvironment that can include cooling air or liquid that removes theheat.

FIG. 3 shows a conventional chassis for housing circuit card assemblies.Referring to FIG. 3, a chassis frame 310 is shown having a number ofchassis grooves 330 for seating a number of circuit cards 340 with theheat spreaders and electronics. The chassis frame 310 has a network ofchassis fins 320 about the perimeter of the chassis frame to provide forheat transfer, which is typically on three sides, such as right, left,and top. When there are multiple cards in the chassis frame, there maybe considerable heat generated by the individual cards such that otherheat transfer features such as heatpipes and vapor chambers may beutilized. In this example, the electronic circuit card is coupled to theheat spreader card which is then inserted into the chassis frame via thegrooves using the wedgelock to secure the card assembly to the chassisframe.

FIG. 4 illustrates one embodiment of the present system that includes anintegrated thermal management system for an electronic circuit card,wherein the integrated system is manufactured by additive manufacturing.As used herein, additive manufacturing refers to processing techniquessuch as 3D printing, rapid prototyping (RP), direct digitalmanufacturing (DDM), selective laser melting (SLM), electron beammelting (EBM), and direct metal laser melting (DMLM).

Referring again to FIG. 4, the integrated thermal management cardassembly 400 in this example includes a heatframe 440, fins 470, cardmounting portion 460 and chassis mounting portion 450 that areintegrally formed as a unitary thermal management structure 480. In thisexample, the card mounting portion 460 integrally formed with theheatframe 440 removes the need for the wedgelock mating of theconventional assembly of FIG. 2. The card mounting portion 460 retainsthe printed circuit card 410 such as by friction fit and/or tongue andgroove. The chassis mounting portion 450 is employed as part of thechassis architecture that is also used to seat circuit cards inserted inslots or channels. As part of ruggedizing this architecture, themounting portion 450 ensures a friction fit in the chassis, so that thecircuit cards do not shake loose from the backplane. It also providespressure between the bottom of the card or heat frame and the chassiswall, thus creating a good thermal bond. In the depicted chassisarchitecture, the traditional wedgelock is superfluous as the elementsare integrally formed and do not insert cards in slots, but stackscircuit cards as slices that are then retained to the I/O module viafasteners, thereby eliminating the traditional wedgelock.

In one example the heatframe 440 is a vapor chamber and the printedcircuit card 410 with the accompanying components 420 are coupled to thevapor chamber. The printed circuit card 410 engages the heatframe 440that is configured to receive the printed circuit card 410. In oneexample, the heatframe 440 includes a tongue and groove feature thatfollows the sides of the circuit card 410. The heatframe 440, in oneexample, is designed for the printed circuit card 410 and theaccompanying heat generating component 420 such that the heatframe 440is designed to be in close proximity to the components 420 on at leastone side. In such an example, the thermal interface material is notrequired or can be minimized.

According to one embodiment, a further feature of the vapor chamberimplementation is a reduction in the Electromagnetic Interference (EMI)of the assembly 480 which allows mating multiple assemblies whileproviding strong attenuation for EMI generated by the electronics orpresent in the external environment.

In addition, the heatframe 440 in one example is designed to be in closeproximity for conductive coupling with not only the upper surface or topof the component 420 but in some examples on one or more sides of thecomponent 420. The ability to effectuate heat transfer over a greatersurface area of the components 420 greatly enhances the thermalmanagement capabilities of the structure 480. In one example theheatframe 440 is conductively coupled to the top surface and at leastone side surface of the component 420. As used herein, conductivelycoupled refers to being in direct, indirect or close proximity to acomponent such that heat transfer can occur. For the indirect contact, amaterial such as a thermal interface material can be utilized.

Thermal performance estimates using thermal resistance of the exemplarythermal management systems illustrated in FIGS. 4 and 6-18 with the 3Dmanufactured vapor chambers indicate they are superior to today's stateof the art systems.

FIG. 5 shows the thermal flow path in a conventional chassis unit withattached circuit card assembly. Specifically, FIG. 5 is a cut away sideperspective and depicts a conventional chassis unit 510 for a circuitcard 520 having components 530 of varying size and shape and is securedto the chassis frame 565 by a wedgelock 560. The thermal flow path in aconventional chassis unit 510 comprising thermal interface material(TIM) 535, heatframe 550, wedgelocks 560 and chassis 565 with attachedcircuit card assembly. TIM 535 is typically used to conduct heat fromthe components 530 to the heat frame 550. At least some of the heat isconveyed by conduction 580 through the heat frame 550 to the chassisframe 565 and finally to the heat fins 570 and dissipated to theenvironment. The wedgelock 560 typically provides a mechanical cammingmechanism that provides mechanical pressure forcing the heat frame 550into intimate contact with at least one side of the groove in thechassis wall, ensuring mechanical retention of the heat frame 550 in thechassis unit 510 and acceptable thermal contact between the matingsurfaces. The wedgelock 560 mechanism occupies space in the chassis walland causes it to be thicker than it would otherwise be, increasing thesize and weight of the overall chassis 510.

In FIGS. 6A and 6B, embodiments of the present system as a modular vaporsystem 600 are illustrated. The depiction in FIG. 6A shows a modularvapor chamber 600 that is custom designed to the circuit card 610 andhaving heat fins 670 to dissipate heat from the electronic components620. The electronic components 620 reside on at least one surface of acircuit card 610 that engages the heatframe 625. The heatframe 625 inthis example is designed to conform to the electronic components 620 tobe in close proximity to the components 620 in order to efficientlyremove heat from the components 620. The heatframe 625 is configured sothe interior component side of the heatframe 625 is sized and shapedabout the components 620 for optimal thermal transfer. In one examplethe circuit card 610 has components 620 on both sides and the heatframe625 on both sides.

Referring to FIG. 6B, a three dimensional (3D) vapor channel chamber 600for a circuit card 610 is depicted in a cut away side perspective view.The modular vapor chamber 600 has a component side 680 that in thisexample is custom designed to conform to the heat generating components620 and optimize heat transfer by being in close proximity to thecomponents. In one example the component side 680 is configured toconduct heat from at least one surface of the components 620, inparticular those that generate the most heat. In another example, thecomponent side 680 is configured to conduct heat from more than onesurface of the components 620 such as the component top surface and oneor more side surfaces. In one embodiment, coupled to the component side680 is a wick structure 650 that helps to direct liquid towards theheated components 620 such as from the receptacle 690 located near thesides. The liquid is converted to vapor by the heated components 620,wherein the vapor absorbs the heat and moves outwards towards thereceptacles 690 where the vapor is converted back into liquid. Thereceptacles 690 provide for further heat transfer such that heat fromthe vapor is removed and turns into liquid.

In one example the modular vapor assembly 600 is integrally formed withthe wick structure 650, the component side 680 and the upper side 675with the vapor chamber formed therebetween and having receptacles 690 onboth sides. The distance between the component side 680 and the opposingupper side 675 of the heatframe 625 is typically at least 0.5 mm and canbe further optimized for the required heat transfer to allow for theliquid to move along the wick surface from the receptacles 690 and forthe vapor to return to the receptacles 690. In this example there are nointernal supports. The integral structure includes the mounting featuresto mate with the circuit card 610.

Referring to FIG. 7, a cut away side view perspective shows oneembodiment of the present system 700 that includes an integral threedimensional (3D) vapor chamber assembly 725 disposed between two circuitcards 710. The two circuit cards 710 each include a number of components720, wherein the cards can be identical cards having the same componentsor different components and layout. The vapor chamber assembly 725includes two component side surfaces 780 with wick structures 750 thatform a vapor channel therebetween. In one example the modular vaporassembly 725 is integrally formed with the wick structure 750 and thevapor chamber 725 formed between the two circuit cards 710 havereceptacles 790 on both sides. In this example there are no internalsupports. Further, the integral structure includes the mounting featuresto mate with the circuit cards 710.

FIG. 8 is an example of a thin modular vapor chamber 810 with variousnon-uniform wick structures. In FIG. 8 the vapor chamber assembly inthis embodiment illustrates a thin vapor chamber 810 with the wickstructures 830 and/or 840 formed on the component side of the vaporchamber. In one example the wick is a non-uniform wick in a thicknessdirection 830. In a further example the wick is a non-uniform wick inthe thickness and planar directions 840. As used herein, the “thickness”refers to dimensions normal to local vapor chamber casing and “planar”refers to dimensions parallel to local vapor chamber casing.

FIG. 9A shows another example of the modular vapor chamber havinginternal supports. FIG. 9B shows the modular vapor chamber embodimentwith off-plane wick structures for enhanced support and fluid flow.Referring to FIGS. 9A and 9B, the modular vapor assembly 900 is depictedshowing internal supports or posts 990 that can be used to enhancestiffness and increase the liquid return. In this example, the modularvapor assembly 900 includes the modular vapor chamber 930 with one ormore posts 990 that add greater stiffness to the assembly. A furtheraspect of the supports 990 is to increase the liquid transport by meansor capillary action. The circuit card 910 includes electronic components920 that generate heat that is conveyed to the vapor chamber 930 due tothe close proximity to at least one side of the vapor chamber 930. Theheat from the component 920 converts the liquid in the vapor chamber 930to vapor that is then conveyed to the receptacles 980 and converted toliquid. The liquid is transported by the wick structure 985 that isformed on the component side of the vapor chamber 930. The posts 990 inthis example are integrally formed wick structures that provide furthercapability to transport the liquid.

FIG. 9C shows another embodiment of the modular vapor chamber embodiment935 with internal support structures 995 that may also serve as feederarteries for the working liquid. The components 920 generate heat thatis transferred to the vapor chamber 935 which causes evaporation of theliquid in the wick structures 985 and converts the liquid to vapor thattravels above the wick structures 985 to the receptacles. The internalsupport structures 995 in one example resemble bridge trusses or otherbio-inspired structures for the vapor chamber case for high strength andlow weight. Typically, the thickness of the vapor chamber case is100-150 microns. However, using support structures such as 995, thevapor chamber case and the wick features can be made thinner, especiallyin proximity of the hot components and enhanced fins to decrease thethermal resistance. The wick structure and the support structures in oneexample are integrally formed by 3D printing or other additivemanufacturing processes.

FIG. 10A-10G depicts various embodiments and structural characteristicsfor the internal supports for the 3D vapor chambers described herein.The internal supports are used, for example, to maintain the shape ofthe vapor chamber and the dimensions for the vapor and liquid transport.While certain embodiments shown herein depict the vapor chamber having awick structure on only one side of the vapor chamber, FIG. 10A shows thevapor chamber 1005 has two component sides 1010 and two porous wickportions 1020 that are on opposing sides and with a vapor space 1030therebetween. Such an embodiment would be used when there are circuitcards with components (not shown) coupled on either side andconductively coupled to the vapor chamber component sides 1010 and withthe vapor space 1030 disposed therebetween.

The vapor chamber in a further embodiment includes internal supportsthat are fabricated via the 3D printing process in numerous designs,number, shapes and sizes such as shown in FIG. 10B-10G. In one example,the supports comprise one or more solid internal support structures withbraces 1045 that can be perpendicular within the vapor chamber case orangled. Another example includes having solid internal supportstructures 1055 that are curved or have a curved portion. In otherembodiments, the internal supports 1065, 1075 include liquid feederarteries to facilitate the liquid transport. For example, the internalsupports can be porous structures that can be straight 1065 or curved1075. Operationally, the supports should be designed such that the vaporchambers can withstand atmospheric pressure at any point of time.Specifically, the vapor chambers should neither break down under highatmospheric pressure nor implode under low atmospheric pressure.Further, the supports should be designed such that the vapor chambers donot affect the overall desired stiffness or rigidity of the chassisassembly.

Various shapes for solid internal supports are shown in FIG. 10B-10D.Referring to FIG. 10B, the internal support and brace 1045 are straightstructures that are internally coupled between the opposite surfaces ofthe vapor chamber 1040. In FIG. 10C, the solid internal supportstructures are angled or curved 1055. FIG. 10D shows an internal supportstructure 1050 without the brace. The internal support in one example ispositioned proximate the heated component(s), sometimes referred to asthe pocket. In another example shown in FIG. 10 E, the solid internalsupport structure includes a vascular or root system for efficientspreading of force/loads and/or liquid.

FIGS. 10F and 10G depict internal support and liquid feeder arteries.The support structures in these examples are porous and allow for liquidand/or air to pass through the structure within the vapor chamber. FIG.10F shows straight porous internal support structures while FIG. 10Gillustrates angled or curved internal support structures.

The number of the internal supports may be dependent upon the designcriteria and factors include the required support for the vapor chambercase and the thermal properties of the various supports. The size andshape for the internal supports also depends upon the design criteriaand thermal/mechanical requirements. Whenever the supports are desiredonly for lending structural strength to the vapor chamber, solidsupports are used. On the other hand, when the supports are desiredadditionally for enhanced cooling of the electronic components, wickstructure is used.

According to one embodiment, there are various wick structures that areemployed with the vapor chamber assemblies. In one example the wickstructures are formed from additive manufacturing processes such as 3Dprinting. The wick structures can be uniform or non-uniform wickstructures in multiple directions. According to one embodiment, the wickstructures are deployed within the internal space of the vapor chamberand also serve as internal support structures.

FIG. 11A-D depicts several examples of the non-uniform wick structure.Specifically, FIG. 11A shows a perspective view of a non-uniform wickstructure 1140 in the thickness direction (z direction). In FIG. 11B,the non-uniform wick structure 1150 in the thickness direction shows thepores 1160, 1165 which in this example has larger size pores 1160proximate the component side of the vapor chamber for transportingliquid. The pores 1165 on the vapor side are of a smaller pore size andtransport the vapor to receptacles in the vapor chamber. The pores inthese examples are round or curved spaces, wherein the curved wickstructure allows for 3D printing in any orientation that allows fornon-planar vapor chambers.

Referring to FIG. 11C, the non-uniform wick structure 1170 is shown inthe thickness and in-plane direction (x-y direction). In FIG. 11D thenon-uniform wick structure 1180 shows further examples of the largerpores 1190 on the liquid transport side and smaller pores 1195 on thevapor transport side.

The structures shown in FIG. 11A-11D are one example of a class ofgeometries by 3D printing in almost any orientation and straightforwardtransitions from larger to smaller pores and vice-versa. The one exampleshown is for circular cylindrical “bore-holes” along the three axes. Itis to be noted that, apart from the cut planes, there are no straightsurfaces in this pore-scale geometry. This attribute is used forbuild-orientation of independent non-uniform wick structures. Thefigures show non-uniform wick structures built on a planar surface, buta further embodiment provides for deforming these wick structures tofollow a curved 3D surface that in one example has a large radius ofcurvature relative to the thickness of the wick structure layer. Theserepresentative wick structures 1140, 1150, 1170, 1180 that are 3Dprinted can be built in numerous orientations, unlike posts or braces,because it is built with curves or arc portions. For example, largeoverhangs cannot be effectively printed without support structures, andthese wick structures allow for internal build supports that can beintegrated with the inner surfaces, namely the vapor side and the casingside of the vapor chamber.

FIG. 12A-12B show modular vapor chamber embodiments with integratedhollow fins. As shown in FIGS. 12A and 12B, the modular vapor chamber1210 is shown according to yet another example. In this example, thevapor chamber fins 1220 are hollow vapor chamber fins, therebypermitting a greater surface area for heat transport. The largecondenser surface area associated with the fins 1220 dramaticallydecreases the contribution of the condensation thermal resistance(temperature drop) in the thermal resistance chain. In anotherembodiment, the hollow fins may be replaced by other heat exchangemechanisms such as an integral fluid heat exchanger or a cold plateinterface coupled to the system.

FIG. 13 shows a thermal management system for electronics 1300 as astacked assembly, including several vapor chambers assemblies 1330,1340, and 1350 with or without circuit cards and assembled along withchassis case portions such as an upper and lower chassis mount to formthe chassis 1300. Referring again to FIG. 13, the modular stackedassembly 1300 includes multiple modular vapor chamber assemblies 1310,1330, 1340, and 1350, each configured to be stacked together to form thelarger unit. In one example the circuit card assemblies 1320 are coupledto respective modular vapor chamber assemblies which are then combinedinto the chassis 1300. As previously described the circuit cards can becoupled to the vapor chamber assemblies such as by friction fit or othersecuring mechanisms. The modular vapor chamber assembly units 1330,1340, and 1350 including any corresponding circuit cards 1320 aresecured to each other by fastening mechanisms such as bolts. There canbe any number of modular vapor chamber assemblies and circuit cardsstacked together and secured as a unitary assembly. The outermostportions of the modular stacked assembly may or may not be coupled tocircuit cards and may be used for packaging and securing the assembliesand circuit cards.

FIG. 14A-D shows an example of forming the stacked modular vaporchambers and corresponding circuit cards assembled into an avionicssystem 1400 with corresponding input output modules 1410. Referring toFIG. 14A, a further depiction of the stacked modular vapor chambers isillustrated with circuit cards 1440 coupled to both sides of a vaporchamber 1430 forming a vapor chamber sandwich 1450. The sandwich 1450shows the vapor chamber 1430 disposed between the electronic circuitcards 1440. As shown in FIG. 14B, the modular vapor chamber sandwich1450 can be stacked with other modular vapor chamber sandwich units andsecured to each other to form a modular electronic assembly 1420. InFIG. 14C, the modular electronic assembly 1420 is electrically coupledto a backplane or input/output modules 1410, forming the final assembly1400 as depicted in FIG. 14D.

As detailed herein, one of the unique attributes of the present systemis a 3D vapor chamber having non-uniform wick structures. A furtheraspect is the collection of individual vapor chambers to form a modularchassis, wherein the circuit cards are aligned and the vapor chambersare stacked to reduce the EMI by isolating the individual vaporchambers.

Other features of the modular chassis stack relate to the mechanicalarchitecture. For example, the ability to configure a chassis with avariable number of ‘slots’ depending on the application, the use of anintegral base plate/air mover (such as synthetic jets or fan). A furtheraspect employs a separable I/O module that is customized to theapplication and environmental requirements.

For example, FIG. 15 shows an embodiment of the thermal managementsystem for an electronic assembly 1500 with enhanced convection usingsynthetic jets 1550 located in at least one of the lower tray 1540 andupper tray 1530 of electronic assembly 1500. In this example the uppertray has fins and considerable access to the external environment forincreased air flow. The synthetic jets 1550 are added to augment theairflow and enhance free convection. The I/O connectors 1510, 1520 inthis example include cut-outs for external air flow such as fromturbines or fans.

FIG. 16A-C shows a modular vapor chamber 1600 in another embodiment thatis integrated into an airframe 1640. Referring to FIG. 16A, theindividual vapor chambers 1610, 1620 and 1630 in the shapes and withstructural supports for the intended application are shown along withthe exterior heat fins. FIG. 16B illustrates the modular vapor chambersassembled into a circular unitary thermal management assembly 1600. FIG.16C shows the thermal management assembly 1600 configured to enablevarious applications such as deployment in an unmanned aerial vehicle1640.

FIG. 17A-C shows thermal management assemblies with different stackingconfigurations of the modular vapor chambers. Referring to FIG. 17A,there are several modular vapor chambers 1710, 1720, 1730 and 1740 withcircuit cards coupled to the chambers that are shaped and sized to formthe thermal management assembly 1750 of FIG. 17B. The circuit cards forthe modular vapor chambers 1720, 1730 are stacked along the length ofthe thermal management assembly 1750 with exterior fins encircling theassembly 1750 for dissipating the heat. FIG. 17C shows a thermalmanagement assembly 1700 with modular vapor chambers having circuitcards radially disposed in a circular form allowing for heat dissipationon all the exterior surfaces.

FIG. 18 shows a thermal management system 1800 as a planar assembly suchas circular, square or rectangular, including two or more partitionedvapor chambers 1810, 1820, 1830 and 1840 planarly assembled to form thechassis of the system 1800. Referring again to FIG. 18, the assembledthermal management system 1800 has a heatframe that includes a number ofpartitioned modules/vapor chambers 1810, 1820, 1830 and 1840 from aplanar perspective. In one example, a typical heatframe unit is replacedby several vapor chambers 1810, 1820, 1830 and 1840 arranged in a planarmanner coupling the vapor chambers with respective circuit cards andassembled to provide thermal and structural support to the thermalmanagement system 1800. In this configuration, even if one of the vaporchambers 1810, 1820, 1830 and 1840 is punctured, the other vaporchambers keep supporting and cooling the electronics. Such a systemstructure supports redundancy and critical mission initiatives.

FIG. 19A-C shows various surface geometries of the 3D vapor chamber toenvelop circuit electronics including conformal, reverse-conformal andcustom-conformal configurations. In one example, the distance or gapbetween the electronic components and the component side of the vaporchamber is 5-12 microns. In FIG. 19A, the thermal management structure1910 is customized such that the component surface geometry of the 3Dvapor chamber 1915 is approximately conformal to the circuit card 1920and components 1925 in maintaining the vapor chamber in close proximityto the components 1925 for efficient heat transfer. In one example thecomponent side of the vapor chamber provide conductive coupling on thetop surface of the components and one or more sides of the components.

In FIG. 19B, the thermal management structure 1940 is customized suchthat the surface side of the 3D vapor chamber 1945 is reverse-conformalto the circuit card 1950 and components 1955 in keeping with designcriteria for integration in the chassis with other cards. In suchconfigurations, the vapor chamber case lifts down and reaches out to theelectronic components 1955. This arrangement in certain applicationsaids in capillary transport of the liquids through the wick structures.

In one further example shown in FIG. 19C, the thermal managementstructure 1960 is customized such that the surface side of the 3D vaporchamber 1965 is custom-fit to the circuit card 1970 and components 1975to increase the heat transfer and optimize the cross section coverage ofthe components 1975 by the vapor chamber 1965 and particularly thecomponents that generate the most heat.

In each of these examples of the thermal management systems 1910, 1940and 1960, the ability to customize the surface geometry of the 3D vaporchambers 1915, 1945 and 1965 to the circuit card components optimizesthe thermal management and allows for higher density of components andcomponents with greater temperatures. The circuit cards 1920, 1950 and1970 and components 1925, 1955 and 1975 in one example have a standardlayout such that multiple boards can be accommodated by a singleheatframe design. In addition, the integral design of correspondingmounting features (not shown) into their respective heatframes (notshown) allows for improved mating with the boards 1920, 1950 and 1970,thereby eliminating the conventional wedgelock. Furthermore, the abilityto integrally design the fins (not shown) and chassis (not shown) to theheatframes (not shown) allows for customization for the intended heatdissipation for specific circuit cards and components. A result of thethermal management structures 1910, 1940 and 1960 that allows forsmaller heatframes when thermal characteristics are not high and forlarger heatframes and fins for components that generate more heat.According to one example, the 3D vapor chambers 1915, 1945 and 1965 inthe integral thermal management structures 1910, 1940 and 1960 are madeusing additive manufacturing technology such as 3D printing.

FIG. 20 shows an alternative configuration of the compartmentalizationof the vapor chamber in a horizontal plane. Referring to FIG. 20, such athermal management system 2000 includes a larger, compartmentalizedvapor chamber 2010. The bigger vapor chamber 2010 is divided intoseveral compartments 2020, 2030, 2040, 2050 and so on using partitions2060, 2070 and so on. The compartments 2020, 2030, 2040, 2050 may beequal or unequal in size depending on the design purpose. Further, eachof the compartments 2020, 2030, 2040, 2050 may be designed to serve/coolthe specific electronics coupled to the respective vapor chambers. Thecompartmentalization of the vapor chambers allows at least some of thevapor chambers to function if one or more compartments are compromised.At the same time, the compartments 2020, 2030, 2040, 2050 share commonboundary walls and are unified by the structural integrity and rigidityof the bigger vapor chamber 2010.

FIG. 21A-F are other examples of the modular vapor chamber withcompliant wall and wick structures. Referring to FIG. 21A, the modularvapor chamber 2100 includes wall (vapor chamber case) 2110 and wickstructures 2130 and 2140. As for the wall 2110, it conforms to the topof the electronic components represented by an angled rectangle 2120.The rectangle 2120 is typically angled/slanted because the electroniccomponents are “tipped” relative to PCB due to manufacturing tolerancesand thus may have a non-horizontal top-profile. Operationally, the vaporchamber case 2110 needs to adapt to the angled top-profile and at leastthat area of the vapor chamber case wall is made compliant. Exaggeratedrepresentation of ridges 2115 in the vapor chamber case 2110 enable thedesired compliance without plastic deformation. In other examples, inaddition to the wall 2110, the wick structures 2140 associated with thecompliant part of the wall 2110 are also made compliant. Referring toFIG. 21A once more, 2130 refers to the plurality of wick structures thatare rigid/non-compliant and 2140 to the plurality of wick structuresthat are compliant. By construction, the wick structures in area 2130are typically connected to each other internally whereas the wickstructures in area 2140 are unconnected. There are various ways thesecomplaint parts of the vapor chamber case 2110 and the wick structures2140 can be permuted and combined as described below.

FIG. 21B represents an example of the modular vapor chamber with wickstructures 2140 having uniform pore size all through and the structureposts 2145 positioned at relatively uniform distance from each other.FIG. 21C represents an example of the modular vapor chamber with wickstructures 2140 having small pores near the top, large pores near thevapor chamber case. In such a configuration, the structure posts 2155are positioned such that there are relatively smaller gaps through thestructures at the top and larger gaps at the bottom. FIG. 21D representsan example of the modular vapor chamber with wick structures 2140 havinglarge pores near top and small pores near the vapor chamber case. Insuch a configuration, the structure posts 2165 are positioned such thatthere are relatively larger gaps through the structures at the top andsmaller gaps at the bottom. Further, referring to FIG. 21E, in the vaporchamber case 2170, compliant and unconnected wick structures 2175 arelocalized only to the component area. Furthermore, referring to FIG.21F, unconnected wick structures line the whole vapor chamber case 2180including the unconnected wick structures 2185 making the whole vaporchamber case 2180 compliant.

In operation, according to one embodiment, the thermal management systemincludes a vapor chamber having a vapor chamber case with a componentside and an opposing vapor side, internal wick structures disposed on atleast the component side, internal working fluid, and additionalinternal support structures. The system in one example is made as asingle unitary structure, wherein the case, wick structures, andinternal support structures are integrally formed during formation by 3Dprinting or other Additive Manufacturing process. The working fluid istypically added to the internal structure until the wick is saturated,then the outer case is sealed. This filling process introduces theworking fluid into the case. In certain examples, some of the fluid willbe in the liquid state, while some may be in the vapor state. When onepart of the thermal management system is thermally connected to a coldreservoir, and another part to a heat source such as electroniccomponents, heat is conducted from the heat source, through adjacentvessel envelope wall, and into the adjacent wick structure which issaturated with liquid. This addition of heat causes the liquid phase ofthe working fluid to boil into the vapor phase within the vessel. Theprocess is similar to that of an operating heat pipe.

In one embodiment, the wick structure is engineered such that very finefeatures are present near the heat source, thus increasing the strengthof the capillary force. However, the fine structures have a high fluidresistance. Therefore, the wick structure between the cold reservoir andheat source is engineered as a coarse structure with smooth featuresthat minimize the fluid resistance. The fine and coarse structures areengineered to maximize the rate of fluid transport, and thus the optimalamount of heat can be transferred.

In another embodiment, the wick structure between the cold reservoir andheat source includes finer structures close to the vapor gap, andcoarser structures close to the vessel wall. The finer structuresprevent the liquid phase of the working fluid passing through the wickfrom interacting with the vapor phase of the working fluid passingthrough the vapor space in the opposite direction. The coarserstructures near the vessel wall allow the liquid to pass through thewick with minimal pressure drop. In one example, the thermal path fromthe electronic component to the cold reservoir is enhanced bytransporting the working fluid (any mix of liquid and vapor) containedwithin the vapor chamber by means of capillary action through anycombination of the wick structure and the internal support structure todissipate heat from the heatframe.

The assembly in one example enhances the thermal capability and theentire structure is fabricated using additive manufacturing technologyto allow for complex geometries that are conformal to the components.Although the figures indicate “pockets” for the hot components, in oneexemplary embodiment the vapor chamber case “conforms” to the hotcomponents via “pockets”, “planes”, or “posts”, as needed. According toone example the wick structure is non-uniform wick oriented in thethickness direction. In another example the wick structure is anon-uniform wick having a thickness and planar directions.

In a thermal management system for circuit cards in a chassis, thecomponents have parasitic heat losses that thermally coupled to thedevice. These losses are removed in order to maintain a proper operatingenvironment for the electronics. In one example the present system movesthe heat from the component such as to cold sink reservoirs, thusmaintaining the component at low temperature.

The present systems reduce the thermal resistance of this thermal pathwhile maintaining or lowering the weight of the system. Certaintechnical advantages of the present system include lower weight, lowerthermal resistance, unlimited shapes and form factors, unitary singlepiece construction. Commercial advantages include custom designs, lowerprice, and more capability and greater thermal elements in the samevolume.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the variousembodiments without departing from their scope. While the dimensions andtypes of materials described herein are intended to define theparameters of the various embodiments, they are by no means limiting andare merely exemplary. Many other embodiments will be apparent to thoseof skill in the art upon reviewing the above description. The scope ofthe various embodiments should, therefore, be determined with referenceto the appended claims, along with the full scope of equivalents towhich such claims are entitled. In the appended claims, the terms“including” and “in which” are used as the plain-English equivalents ofthe respective terms “comprising” and “wherein.” Moreover, in thefollowing claims, the terms “first,” “second,” and “third,” etc. areused merely as labels, and are not intended to impose numericalrequirements on their objects.

Further, the limitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. § 112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure. It is to be understood that notnecessarily all such objects or advantages described above may beachieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the systems andtechniques described herein may be embodied or carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other objects or advantagesas may be taught or suggested herein.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the disclosuremay include only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

1.-20. (canceled)
 21. A thermal management system, comprising: a hollowvapor chamber configured to contain a working fluid that conducts heatfrom a heat source to a cold reservoir, the hollow vapor chamber havingan interior defining a vapor space to contain a vapor of the workingfluid and having a non-porous exterior wall and a porous wick structureintegrally formed with the solid exterior wall by an additivemanufacturing process, the porous wick structure being in the interiorof the hollow vapor chamber, wherein the non-porous exterior wall has acomponent side surface configured to be thermally coupled to a heatgenerating component of the heat source, the component side surfacehaving a shape that at least partially conforms to at least one surfaceof the heat generating component, and a portion of the porous wickstructure opposite the component side surface of the solid exterior walldirects the working fluid toward the heat generating component.
 22. Thethermal management system of claim 21, wherein the hollow vapor chamberfurther comprises a condenser integrally formed by the additivemanufacturing process.
 23. The thermal management system of claim 22,wherein the condenser comprises a plurality of hollow fins integrallyformed with the hollow vapor chamber by the additive manufacturingprocess.
 24. The thermal management system of claim 23, wherein theplurality of hollow fins are in fluidic communication with the vaporspace.
 25. The thermal management system of claim 21, wherein the porouswick structure has one or more of a non-uniform thickness, a non-uniformporosity, a non-uniform pore-size, or non-uniform permeability.
 26. Thethermal management system of claim 21, wherein the integrally formedvapor chamber comprises integrally formed internal support posts formedby the additive manufacturing process that extends between opposingsides of the integrally formed vapor chamber.
 27. The thermal managementsystem of claim 26, wherein the integrally formed internal support postscomprise porous wick structures.
 28. The thermal management system ofclaim 26, wherein the integrally formed support posts comprisenon-porous solid portions and porous wick structures.
 29. The thermalmanagement system of claim 26, wherein pores of the wick structures ofthe integrally formed internal support posts that are adjacent theopposing sides of the integrally formed vapor chamber are larger thanpores that are between the opposing sides.
 30. The thermal managementsystem of claim 26, wherein the integrally formed support posts arecurved.
 31. The thermal management system of claim 21, wherein pores ofthe porous wick structure on a liquid transport side adjacent thenon-porous solid exterior wall are larger than pores on a vaportransport side adjacent the vapor space.
 32. The thermal managementsystem of claim 21, wherein the integrally formed vapor chambercomprises a plurality of ridges that permit elastic deformation of theintegrally formed vapor chamber.
 33. The thermal management system ofclaim 21, wherein the component side surface of the non-porous solidexterior wall is non-planar.
 34. The thermal management system of claim21, wherein the component side surface includes a mounting portion thatis configured to retain the heat generating component of the heatsource.
 35. The thermal management system of claim 34, wherein themounting portion retains the heat generating component by a frictionfit.
 36. The thermal management system of claim 21, wherein the additivemanufacturing process comprises 3D printing, rapid prototyping, directdigital manufacturing, selective laser melting, electron beam melting,or direct metal laser melting.